Jane,
I’m a bit (well, a big bit) confused. Since you installed 10.4.10, a 10.3.9 upgrade would only be regressive (not an update) besides which, I don’t think it would or should work. And apparently it doesn’t.
Since you installed 10.4.10, you have the most recent Safari, v2.0.4 (419.3), unless of course, you’re trying to install the Safari Beta v3.0.2. FWIW, many have had problems with this beta, some quite serious, so I don’t recommend it.
Please provide the link, or more data, on what it is you’re trying to install.
I don't mean to be abrupt, I just don't understand what you want upgraded/installed.